The present invention relates to a scroll compressor and a refrigerating system (such as an air-conditioner or a refrigerator) using an ammonia group refrigerant.
A carbon fluoride group refrigerant such as HCFC or CFC which has been conventionally used for a refrigerating system causes earth ozonospheric destruction or global warming, and accordingly, the use of natural refrigerant such as ammonia group refrigerant is desirable. However, the ammonia group refrigerant is combustible and toxic, and further, it is highly corrosive. Accordingly, it cannot be used for a refrigerating system incorporating a copper wire or an organic material.
In a conventional compressor using an ammonia group refrigerant, a compression mechanism portion coupled with a motor portion by a coupling incorporates a mechanical shaft seal assembly for a rotary shaft thereof in order to prevent the refrigerant from leaking between the shaft and the compression mechanism portion, and to seal against the atmosphere. However, it has been difficult to completely prevent the leakage of refrigerant gas and to seal against the atmosphere. Further, large mechanical loss has been caused.
Recently, there has been proposed, as disclosed in JP-A-2000-83339, a compressor having a hermetic type sealed structure in which a compression portion and a motor portion are integrally incorporated with each other, windings for a motor are made of high purity aluminum and are covered with fluororesin which is chemically stable against ammonia. Further, as disclosed in JP-A-10-112949, there has been also proposed such a compressor that a compression portion and a naked motor are accommodated in a hermetic chamber, various parts of the motor being coated thereover with resin materials, and windings in the motor are formed of Ni-plated copper wires or Sn-plated copper wires and are soaked in ether group lubrication oil which is compatible with ammonia so as to prevent direct contact with ammonia.
In the above-mentioned technology using ammonia refrigerant, a screw type or rotary type compressor which is of enclosed type has been developed. Such an enclosed type compressor inevitably requires a covering member for protecting windings of a motor from ammonia, and a molding member for suppressing vibration, and accordingly, cooling therefore is difficult. Further, torsional vibration of a shaft is caused due to interaction between load torque pulsation on the compressor side and electromagnetic pulsation (vibration) caused by electromagnetically exciting force on the motor side, resulting in a risk of burning the motor portion due to electromagnetic pulsation thereby. Further, an ammonia group refrigerant causes a discharge refrigerant temperature to be higher than that of a conventionally used carbon fluoride group refrigerant such as HCFC or CFC refrigerant, resulting in a risk of deteriorating refrigerator oil. Thus, the compressor using ammonia refrigerant has not yet been practically used at present.
Further, in the case of using an aluminum electric wire is used for windings in a motor, the aluminum wire has an electroconductivity which is lower than that of a copper wire, and accordingly, a heat generation value from the motor windings becomes higher, and accordingly, there has been raised such a problem that the temperature of the motor portion becomes higher.
Further, in the case of using fluororesin as a coating material for motor windings, since the fluororesin has a high mold-releasability and nonadhesiveness, the adherence thereof with respect to the motor windings is low, thereby it has been found a risk of burning the motor portion.
An object of the present invention is to provide a scroll compressor and a refrigerator using ammonia group refrigerant which can ensure a certain reliability that causes a problem as to a hermetic type compressor using ammonia group refrigerant, and which can be used under an ammonia atmosphere.
Another object of the present invention is to provide a scroll compressor and a refrigerator using ammonia group refrigerant, with a high degree of efficiency.
To this end, according to a first aspect of the present invention, there is provided a scroll compressor using ammonia group refrigerant, having a hermetic chamber, and comprising, in the hermetic chamber, a scroll compression mechanism portion in combination of an orbiting scroll and a fixed scroll, a motor portion for driving the compression mechanism portion and a frame for supporting the compression mechanism portion, at least either one of the frame and a stator of the motor drive portion being made into close contact with the inner peripheral surface of the hermetic chamber, wherein ammonia group refrigerant is used, and aluminum wires coated thereover with fluororesin is used for windings of the motor portion.
In the above-mentioned aspect, the windings of the motor portion, are preferably formed of aluminum wires which are subjected to chemical conversion coating of a fluorine compound and are then coated thereover with the fluororesin, and in particular, the outer surfaces of the aluminum wires subjected to the chemical conversion coating may be roughened in order to enhance the adhesion of the fluororesin with which the aluminum wires are coated thereover. Alternatively, the fluororesin with which the aluminum wires are coated, is subjected to photochemical reaction with the use of amine compound, and the fluororesin as a covering material is subjected to surface reforming, in order to enhance the adhesion of the aluminum wires to the covering material.
Further, if coil ends in the motor portion are molded with dicyclopentadiene, the vibration of the motor windings can be suppressed. Further, motor stator windings which are concentrically wound can enhance the molding efficiency at the coil end thereof. Further, a DC brushless motor is used in the motor portion, thereby it is possible to enhance the efficiency so as to restrain heat-generation of the motor portion.
Further, according to a second aspect of the present invention, there is provided a refrigerator using ammonia group refrigerant incorporating a scroll compressor and a condenser, the scroll compressor according to the first aspect of the present invention being also used as the scroll compressor in this aspect, and a liquid injection circuit for supplying ammonia group liquid refrigerant into a compression room of the compression mechanism portion of the scroll compressor.
According to a third aspect of the present invention, there is provided a refrigerator including a scroll compressor using ammonia group refrigerant having a hermetic chamber and comprising, in the hermetic chamber, a scroll compression mechanism portion in combination of an orbiting scroll and a fixed scroll and a motor portion for driving the compression mechanism portion, the motor portion having windings formed of aluminum wires which are coated thereover with fluororesin, wherein the motor portion is cooled by discharged refrigerant gas from the compression mechanism portion before the refrigerant gas is fed outside of the hermetic chamber, a condenser for condensating the refrigerant discharged from the scroll compressor, a liquid receiver provided down-stream of the condenser, and a liquid injection circuit for feeding liquid refrigerant from the liquid receiver into a compression room of the scroll compressor.
In this configuration, there is preferably provided an injection valve or an electronic expansion valve in the above-mentioned liquid injection circuit, the injection valve or the expansion valve being controlled so as to adjust the quantity of liquid injection in accordance with a discharge side temperature of the scroll compressor.
With this configuration in which liquid injection is made for the compressor, the temperature of refrigerant fluid can be restrained during compression, and accordingly, it is possible to eliminate such a disadvantage that the efficiency of the compressor is lowered as the temperature of the refrigerant discharged from the compressor is increased in the case of a compressor using ammonia group refrigerant. That is, according to the present invention, the temperature of the refrigerant is restrained from becoming high, thereby it is possible to enhance the efficiency of the compressor. In particular, in the case of using a motor which incorporates aluminum electric wires, and with which the value of heat generation tends to be high, the configuration in which the motor incorporated in, for example, in a hermetic type compressor is cooled by discharged gas from the compressor, can cool the motor with the discharged gas whose temperature is lowered through liquid injection, thereby it is possible to exhibit such a technical effect that the motor can be efficiently lowered. Further, according to the present invention, the scroll compressor is used, and accordingly, the liquid injection can be simply carried out in comparison with the other compressors, Further, with the use of the scroll compressor, variation in the torque of the compressor can be restrained to a small value, and accordingly, electromagnetic vibration can be reduced, thereby it is possible to enhance the reliability.